The invention concerns a method for control and regulation of the drive system of a motor vehicle.
Drive systems known from the practice each comprise a prime mover and a mechanical or automatic transmission situated between the prime mover and the output of a motor vehicle. The drive system usually has an electronic control system to make available the most comfortable possible mode of operation of the drive system to the driver which, together with other control units, comprises an electronic transmission control, such as for an automatic transmission, and connected therewith an electronic engine control for a prime mover via adequate interfaces.
The function of electronic transmission controls of automatic transmissions is to unburden the driver and, in so doing, select an optimal ratio for the existing driving situation in regard to consumption, performance and comfort. The electronic transmission control mainly carries out the selection of the most favorable gear and the control of the shifting cycle, the selection being performed according to different parameters. One such parameter for this is constituted by the engine torque which, in the control systems known from the practice, can be directly relayed to the electronic transmission control and used for gear selection. Alternatively to this, the torque can be separately determined also from other measured values fed to the engine, such as the throttle valve position or the air mass. The driving situation, the kind of gear change and the road speed are further taken into account when effecting the pressure control of the clutches of the transmission and their adaptation to the torque to be transmitted. In this manner, the control system engages with good shifting comfort the appropriate gear according to the transmission output rotational speed and the engine load optionally under self-adaptive accommodation to the driving style of a driver and existing traffic situation.
In gear shifts, that is, in a gear change or change over from a neutral position to a certain ratio of the transmission, distinction is made according to the existing operating point in coasting or braking shifts, the same as in load shifts. As load shifts are designated here all shifts in a power flow from the prime mover to the output of a motor vehicle while braking or coasting shifts designate all shifts where the input results from the potential or kinetic energy of the vehicle going from the output of the vehicle toward the engine.
However, in the already known drive systems, a control of a gear shift in the coasting operation often proves uncomfortable, especially since when initiating a shift at high road speeds in the coasting operation, an engine rotational speed is lower than a transmission rotational speed and a restoration of the power flow of the drive train of the drive system results in a not inconsiderable deceleration of the vehicle. The deceleration of the vehicle is caused by the need of kinetic energy for acceleration of the rotatory masses of engine and transmission.
Besides, in the coasting operation there occurs over an engaging clutch a consideration loading of the clutch due to the high acceleration of the rotatory masses of the engine, since to prevent damages to comfort, the admissible vehicle deceleration that appears is limited and the limitation is adjusted by a prolongation of the gridding time of the engaging clutch.
The problem on which this invention is based is to provide a method for control and regulation of a drive system of a motor vehicle having an electronic transmission control for an automatic transmission with which method a vehicle deceleration in the coasting operation can be limited during a gear shift and at the same time a load of the clutch can be considerably reduced.
With the inventive method, in which the rotatory masses of the engine are regulated and/or accelerated under control to limit a deceleration of the vehicle in a coasting operation of the drive system, the acceleration energy needed can be advantageously applied by the engine itself.
By the inventive positive engagement of the engine, it is also possible during a change over of a transmission element from an open to a closed or a slipping state in a coupling operation of the transmission and/or a regulation operation of the transmission element in the coasting operation, to advantageously adjust an applicable curve of the vehicle deceleration wherein the vehicle deceleration can be retained approximately below a presettable tolerance value to implement a very comfortable shifting behavior.
By virtue of the inventive regulated and/or controlled acceleration of the rotatory masses of the engine during the coupling procedure of the transmission or the regulating procedure of the transmission element, additionally there results the possibility of implementing an applicable deceleration increase in such a manner that a driver with otherwise great shifting comfort perceives the deceleration as feedback of the vehicle and a power flow of the drive system or of the drive train is again produced between an output of the vehicle and the engine.
By virtue of the regulated and/or controlled accelerations of the rotatory masses of the engine in the coasting operation during a coupling procedure of the transmission, there further results the advantage that coupling procedures in the coasting operation can be carried outing a large rotational speed range, especially even at high rotational speeds of the output, without reduction of the driving comfort.
One other advantage is that a coupling procedure of the transmission or a regulating procedure of the transmission element also means no reduction of the driving safety, since a jack-knifing of the vehicle resulting from too great a deceleration of the speed can be eliminated by a uniform, especially limited, deceleration of the vehicle even in special programs such as a winter drive program.
The expression xe2x80x9ctransmission elementxe2x80x9d used here stands for a shiftable clutch which to produce or increase the power flow in the drive system is closed, brought to a slipping state or opened. By the expression xe2x80x9ctransmission elementxe2x80x9d is further to be understood also a regulated lock-up clutch of a converter of an automatic transmission which likewise is changed over from open to closed or slipping state according to the existing operating situation of the drive system.
Taking into consideration this interpretation of the expression xe2x80x9ctransmission elementxe2x80x9d, there further results the advantage that with the inventive method much shorter shifting times with simultaneous increased driving comfort can be implemented during coupling or gear initiation, the same as during a regulation procedure of the lock-up clutch.